Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...

I tried to get out of the diagonal the adapter holding the last filter (~Etalon).

I removed the hex screws on both sides (they are put back on the here picture, sorry).
Then I tried to get out this adapter, but it doesn't come out (It doesn't move at all...).
Has anyone removed it?
Is it glued?

I see on this adapter: three holes of ~2mm in diameter, located 120°.
One is marked with the arrow.
Do you have any idea for their use?